Method and apparatus for simultaneous support of fast restoration and native multicast in ip networks

ABSTRACT

The invention includes a method and apparatus for simultaneously supporting restoration and native multicast at a router in an Internet Protocol (IP) network. In one embodiment, a method includes establishing a point-to-point pseudowire having an endpoint at the router, associating the point-to-point pseudowire with an IP interface, and associating a multicast protocol with the IP interface. The point-to-point pseudowire is adapted for supporting restoration in response to a failure. The association of the multicast protocol with the IP interface enables running of the multicast protocol in a manner that gives an appearance that the multicast protocol is running natively on an IP link. This methodology may be repeated for each of a plurality of routers in an IP network in order to configure the routers to support restoration capabilities and native multicast capabilities such that fast restoration may be provided in response to failure conditions in a manner that is transparent to a multicast protocol providing multicast capabilities for the IP network. In this manner, both fast restoration and native multicast may be supported within an IP network, e.g., in an IPTV network or other types of IP networks supporting other types of services.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/948,281, filed Jul. 6, 2007, which is incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The invention relates to the field of communication networks and, morespecifically, Internet Protocol (IP) multicast networks.

BACKGROUND OF THE INVENTION

In Internet Protocol (IP) Television (IPTV) networks, two primaryrequirements must be satisfied by the underlying network in order forservices to be delivered effectively: fast restoration and efficientmulticast. The fast restoration requirement is needed in order forservices to converge quickly in response to a failure. In IPTV networks,restoration is typically required to be performed in less than 50 ms.The efficient multicast requirement is needed in order to controlconsumption of network resources. In IPTV networks, there may behundreds of high-bandwidth television channels that need to bedistributed from a few content sources to potentially millions ofcontent subscribers and, thus, replication of television channels formulticast purposes must be performed as close to the content subscribersas possible in order to minimize consumption of network resources.

In IP networks, Multiprotocol Label Switching (MPLS) is often used toprovide fast restoration capabilities and Protocol Independent Multicast(PIM) is used to provide multicast capabilities. In existing IPnetworks, however, MPLS and PIM cannot be used together because manyproblems result. First, the PIM Reverse Path Forwarding (RPF) check doesnot account for MPLS Label Switched Paths (LSPs). Second, even where thePIM RPF checks are successful, this results in multiple OutgoingInterfaces in the Outgoing Interface List (OIL) for multicastreplication, and, consequently, multiple point-to-multipoint (P2MP) LSPsare required, thereby complicating provisioning and restorationprocesses. Third, network convergence after a link failure would take aslong as the combined unicast protocol convergence and subsequentmulticast protocol convergence (i.e., on the order of seconds).

As described herein, due to the competing considerations of the MPLS andPIM protocols, MPLS and PIM currently cannot be used together inexisting IP networks, and, thus, there is no known IP networkimplementation which can satisfy these requirements for IPTV networks.

SUMMARY OF THE INVENTION

Various deficiencies in the prior art are addressed through a method andapparatus for simultaneously supporting restoration and native multicastat a router in an Internet Protocol (IP) network. In one embodiment, amethod includes establishing a point-to-point pseudowire having anendpoint at the router, associating the point-to-point pseudowire withan IP interface, and associating a multicast protocol with the IPinterface. The point-to-point pseudowire is adapted for supportingrestoration in response to a failure. The association of the multicastprotocol to the IP interface enables running of the multicast protocolin a manner that gives an appearance that the multicast protocol isrunning natively on an IP link. This methodology may be repeated foreach of a plurality of routers in an IP network in order to configurethe routers to support restoration capabilities and native multicastcapabilities such that fast restoration may be provided in response tofailure conditions in a manner that is transparent to a multicastprotocol providing multicast capabilities for the IP network. In thismanner, both fast restoration and native multicast may be supportedwithin an IP network, e.g., in an IPTV network or other types of IPnetworks supporting other types of services.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 depicts a high-level block diagram of a communication network;

FIG. 2 depicts a high-level block diagram of the communication networkof FIG. 1, showing reaction of the communication network to a failure;

FIG. 3 depicts a method according to one embodiment of the invention;

FIG. 4 depicts a method according to one embodiment of the invention;

FIG. 5 depicts a method according to one embodiment of the invention

FIG. 6 depicts a high-level block diagram an exemplary ring-within-ringcommunication network; and

FIG. 7 depicts a high-level block diagram of a general-purpose computersuitable for use in performing the functions described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION OF THE INVENTION

The present invention enables simultaneous support of fast restorationand native multicast in IP networks. Although primarily depicted anddescribed herein within the context of IPTV networks, the presentinvention may be used simultaneous support of fast restoration andnative multicast in various other types of IP networks supporting othertypes of service.

FIG. 1 depicts a high-level block diagram of a communication network.Specifically, communication network 100 includes a plurality of routers110 _(A)-110 _(D) (collectively, routers 110) arranged in a ringtopology, where adjacent ones of the routers 110 are connected usingrespective pairs of physical links. Although depicted as being directlyconnected, it will be appreciated that the connections between adjacentones of the routers 110 may traverse various other physical elementswhich are ignored herein for purposes of clarity in depicting anddescribing simultaneous use of fast restoration capabilities andmulticast capabilities in IP networks.

As depicted in FIG. 1, routers 110 _(A) and 110 _(B) are connected usinga first pair of physical links 111 ₁₁ and 111 ₁₂ (collectively, physicallinks 111 ₁), routers 110 _(B) and 110 _(C) are connected using a secondpair of physical links 111 ₂₁ and 111 ₂₂ (collectively, physical links111 ₂), routers 110 _(C) and 110 _(D) are connected using a third pairof physical links 111 ₃₁ and 111 ₃₂ (collectively, physical links 111₃), and routers 110 _(D) and 110 _(A) are connected using a fourth pairof physical links 111 ₄₁ and 111 ₄₂ (collectively, physical links 111₄). The physical links in the pairs of physical links 111 ₁-111 ₄ may becollectively referred to as physical links 111. In one embodiment,physical links 111 are Packet over SONET/SDH (POS) links. In oneembodiment, physical links 111 are Ethernet links. The physical links111 may be implemented using other types of physical links.

As depicted in FIG. 1, pairs of point-to-point (P2P) pseudowires (PWs)are established between adjacent ones of the routers 110. A first pairof P2P PWs 112 ₁₁ and 112 ₁₂ (associated with respective physical links111 ₁₁ and 111 ₁₂) is established between routers 110 _(A) and 110 _(B).A second pair of P2P PWs 112 ₂₁ and 112 ₂₂ (associated with respectivephysical links 111 ₂₁ and 111 ₂₂) is established between routers 110_(B) and 110 _(C). A third pair of P2P PWs 112 ₃₁ and 112 ₃₂ (associatedwith respective physical links 111 ₃₁ and 111 ₃₂) is established betweenrouters 110 _(C) and 110 _(D) A fourth pair of P2P PWs 112 ₄₁ and 112 ₄₂(associated with respective physical links 111 ₄₁ and 111 ₄₂) isestablished between routers 110 _(D) and 110 _(A) The P2P PWs in thepairs of P2P PWs 112 ₁-112 ₄ may be collectively referred to as P2P PWs112.

The P2P PWs 112 are unidirectional P2P PWs. In one embodiment, each ofthe P2P PWs 112 established between adjacent routers 110 may beestablished in one direction (e.g., each of the P2P PWs 112 is operatingin a clockwise direction, as depicted in FIG. 1). Although primarilydepicted and described herein with respect to an embodiment in whicheach of the P2P PWs is established in one direction, in otherembodiments P2P PWs may be established using multiple directions (e.g.,depending on factors such as the desired configuration of the network,the need for multicast flows in particular directions, interconnectionsbetween ring networks to form ring-within-ring networks, and the like,as well as various combinations thereof).

The P2P PWs 112 provide logical paths between routers 110. The P2P PWs112 may be implemented using any technology capable of supporting fastrestoration capabilities. In one embodiment, for example, P2P PWs 112are implemented as P2P Multi-Protocol Label Switching (MPLS) PWs. In onesuch embodiment, MPLS Fast Reroute (FRR) capabilities are used toprovide link protection (e.g., for physical links 111 ) and nodeprotection (e.g., for routers 110) via fast detection and recoverycapabilities, thereby providing fast restoration from failures. In oneembodiment, fast restoration is the capability to recover from a failurein less than 50 ms (although fast restoration may be defined using othertime requirements, e.g., depending on the service(s) for whichrestoration is supported).

In one embodiment, in order to support fast restoration using MPLS FRRcapabilities, a primary path and a secondary path (e.g., primary andsecondary LSPs) are provisioned for each P2P PW 112. The primary andsecondary LSPs may be statically pre-provisioned, dynamicallyprovisioned (e.g., calculated using the Constrained Shortest Path First(CSPF) algorithm or other dynamic algorithms), and the like, as well asvarious combinations thereof. In one embodiment, the primary andsecondary LSPs may be established automatically (e.g., via the ResourceReservation Protocol (RSVP) signaling protocol or any other protocolscapable of automatically establishing LSPs).

As described herein, each P2P PW 112 is associated with a pair oflogical IP interfaces (i.e., each end of each P2P PW 112 is associatedwith a logical IP interface). As depicted in FIG. 1, a first endpoint ofP2P PW 112 ₁₁ between routers 110 _(A) and 110 _(B) is associated with alogical IP interface 113 _(11A) on router 110 _(A) and a second endpointof P2P PW 112 ₁₁ between routers 110 _(A) and 110 _(B) is associatedwith a logical IP interface 113 _(11B) on router 110 _(B) . Similarly, afirst endpoint of P2P PW 112 ₁₂ between routers 110 _(A) and 110 _(B) isassociated with a logical IP interface 113 _(12A) on router 110 _(A) anda second endpoint of P2P PW 112 ₁₂ between routers 110 _(A) and 110 _(B)is associated with a logical IP interface 113 _(12B) on router 110 _(B).A pair of logical IP interfaces 113 is logically associated with each ofthe other P2P PWs 112. The logical IP interfaces in the pairs of logicalIP interfaces 113 ₁-113 ₄ may be collectively referred to as logical IPinterfaces 113.

In other words, the endpoints of each P2P PWs 112 are IP-basedinterfaces. In this manner, P2P PWs 112 provide logical paths (e.g.,providing MPLS paths, where the P2P PWs 112 are MPLS PWs) over IP paths(i.e., since the P2P PWs 112 are associated with logical IP interfaces113). In one embodiment, logical IP interfaces 113 are service-enabledIP interfaces. In one such embodiment, for example, logical IPinterfaces 113 are Internet Enhancement Service (IES) interfaces. Thelogical IP interfaces 113 may be implemented using other types ofservice-enabled IP interfaces.

As described herein, a multicast protocol is running on the logical IPinterfaces 113 of routers 110 (rather than running on native IPinterfaces of routers 110). The multicast protocol runs on the logicalIP interfaces 113 by binding the multicast protocol to the logical IPinterfaces 113, which are logically associated with the P2P PWs 112,respectively. In this manner, it appears that the multicast protocol isrunning natively across native IP links between routers 110. Themulticast protocol may be any multicast protocol (e.g., such as ProtocolIndependent Multicast (PIM) and/or like multicast protocols).

Thus, the configuration depicted and described with respect to FIG. 1enables simultaneous support of native multicast (using any multicastprotocol, such as PIM) and fast restoration (using any protocol capableof delivering fast restoration, such as MPLS).

In one embodiment, Equal-Cost Multi-Path Routing (ECMP) is utilized inorder to enable each router 110 to utilize both of the logical IPinterfaces 113 in each pair of logical IP interfaces 113.

In one embodiment, ECMP enables each router 110 to utilize both logicalIP interfaces 113 in each pair of logical IP interfaces 113 by sharingdestination reachability information over two next-hops.

In one embodiment, ECMP enables each router 110 to utilize both logicalIP interfaces 113 in each pair of logical IP interfaces 113 for aMulticast PIM Join by sharing source reachability over two reverse pathforwarding interfaces (i.e., toward the same source). In one suchembodiment, the normal round robin mechanism of the PIM Join is replacedby an implementation in which the PIM Join is distributed round robinbased on the number of multicast groups on each of the available logicalIP interfaces 113. For example, if a first logical IP interface 113 hasthree multicast groups and a second logical IP interface 113 has fourmulticast groups, the first logical IP interface 113 will be chosenfirst because the first logical IP interface 113 has less multicastgroups than the second logical IP interface 113.

In one embodiment, in order for the logical IP interface 113 of a givenP2P PWs 112 to be chosen in a unicast routing table of the associatedrouter 110, the logical IP interface 113 must have a lower routing costthan the native IP interface of that associated router 110. This furtherensures that the multicast source reachability of the multicast protocoluses the logical IP interface 113 of router 110, rather than using thenative IP interface of router 110.

FIG. 2 depicts a high-level block diagram of the communication networkof FIG. 1, showing reaction of the communication network to a failure.

For the example of FIG. 2, assume that a multicast flow exists fromrouter 110 _(A) to router 110 _(B). The multicast flow from router 110_(A) to router 110 _(B) transports IP packets from router 110 _(A) torouter 110 _(B). The multicast flow is using logical IP interface 113_(12A) on router 110 _(A) and logical IP interface 113 _(12B) on router110 _(B), which are each associated with P2P PW 112 ₁₂ established forphysical link 111 ₁₂. In this example, assume that fast restorationbetween routers 110 is provided using MPLS and multicast distribution ofIP packets between routers 110 is provided using PIM.

For the example of FIG. 2, further assume that physical link 111 ₁₂supporting the multicast flow fails (denoted as failure condition 210).As a result of failure condition 210, P2P PW 112 ₁₂ established forphysical link 111 ₁₂ also fails. The router 110 _(A) detects failurecondition 210 and, using MPLS fast restoration, restores communicationbetween router 110 _(A) and router 110 _(B) by rerouting the P2P PW 112₁₂ between router 110 _(A) and router 110 _(B). As depicted in FIG. 2,the MPLS-based fast restoration restores communication between interface113 _(12A) on router 110 _(A) and logical IP interface 113 _(12B) byrerouting the P2P PW 112 ₁₂ in the opposite direction between router 110_(A) and router 110 _(B). The P2P PW 112 ₁₂ is rerouted in the oppositedirection using physical links 111 ₄₂, 111 ₃₂, and 111 ₂₂. This isdenoted as rerouted P2P PW 112 ₁₂ (denoted using a dashed line). Thus,the multicast flow between router 110 _(A) and router 110 _(B) continuesto be supported.

Thus, MPLS-based fast restoration restores logical IP interface 113_(12A) on router 110 _(A) and restores logical IP interface 113 _(12E)on router 110 _(B). From the perspective of the PIM protocol, theexisting multicast flow follows the same logical path after the failurecondition 210 as was followed prior to the failure condition 210 (i.e.,flowing from source router 110 _(A) to destination router 110 _(B)).Thus, due to the fast restoration provided by MPLS, the failurecondition 210 is transparent to the PIM protocol (because the minimumPIM Hello timer is one second and the PIM Hold timer to detect thefailure of a link is three seconds, both of which are significantlylonger than the time required for MPLS-based fast restoration to reroutethe P2P PW 112 ₁₂ to restore the logical IP interfaces 113 _(12A) and113 _(12B) after the failure condition).

As an example, consider an IP network that is using MPLS and PIM totransmit packets from a router in New York to a router in Los Angelesvia a router in Chicago.

In this example, in an IP network that is attempting to use MPLS and PIMwithout the present invention, for a packet being transmitted from therouter in NY to the router in LA via the router in Chicago using an MPLSLSP established from the router in NY to the router in LA, the router inLA is not aware that the packet is traversing the router in Chicago(i.e., it appears to the router in LA that the packet is receiveddirectly from the router in NY). However, the PIM Reverse PathForwarding (RPF) check performed by the router in LA upon receiving thepacket will indicate to the router in LA that it should have receivedthe packet from the router in Chicago rather than from the router in NY(since the PIM RPF check does not account for MPLS LSPs). This resultfrom the PIM RPF check is due to the fact that PIM is operating toensure that the most efficient multicast replication of packets is beingrealized. In this case, the router in LA will drop the packet from NYeven though there is no problem with the packet. In other words, an IPnetwork that is attempting to use MPLS and PIM without the presentinvention will not operate properly.

In this example, in an IP network according to the present invention,since MPLS point-to-point pseudowires are established between adjacentones of the routers (e.g., between the router in NY and the router inChicago, between the router in Chicago and the router in LA, and betweenthe router in LA and the router in NY) the router in LA is aware thatthe packet is traversing the router in Chicago. Thus, the PIM RPF checkperformed by the router in Los Angeles upon receiving the packet will besuccessful (i.e., the PIM RPF check will indicate to the router in LAthat it should have received the packet from the router in Chicago, andthe router in LA is in fact aware that the packet is being received fromthe router in NY indirectly via the router in Chicago). In other words,the present invention enables simultaneous use of MPLS and PIM within anIP network. Thus, the present invention enables simultaneous support offast restoration (e.g., using MPLS, as in this example, or any otherprotocol supporting fast restoration capabilities, as described herein)and multicast (e.g., using PIM, as in this example, or any otherprotocol supporting multicast capabilities, as described herein).

FIG. 3 depicts a method according to one embodiment of the presentinvention. Specifically, method 300 of FIG. 3 includes a method forforming an IP network supporting fast restoration using a restorationprotocol and native multicast capabilities using a multicast protocol.Although primarily depicted and described herein as being performedserially, at least a portion of the steps of method 300 may be performedcontemporaneously, or in a different order than depicted and describedwith respect to FIG. 3. The method 300 begins at step 302 and proceedsto step 304.

At step 304, a segment between routers (denoted as a first router and asecond router) is selected. At step 306, a physical link of the segmentis selected. At step 308, a P2P PW is established for the physical linkof the segment.

At step 310, a first endpoint of the established P2P PW is associatedwith an IP interface of the first router. At step 312, a second endpointof the established P2P PW is associated with an IP interface of thesecond router.

At step 314, the multicast protocol is associated with the IP interfaceassociated with the P2P PW on the first router (i.e., bound to the IPinterface associated with the P2P PW). At step 316, the multicastprotocol is associated with the IP interface associated with the P2P PWon the first router (i.e., bound to the IP interface associated with theP2P PW).

At step 318, a determination is made as to whether or not the selectedsegment is complete (e.g., whether or not additional P2P PWs will beestablished between that pair of routers). If the selected segment isnot complete, method 300 proceeds to step 318, at which point the nextphysical link of the segment is selected, and, from step 318, returns to308 such that a P2P PW may be provisioned for another physical linkconnecting the first router and the second router over the selectedsegment). If the selected segment is complete, method 300 proceeds tostep 322.

At step 322, a determination is made as to whether or not the network iscomplete (e.g., whether or not all segments between routers have beenconfigured to support restoration and multicast capabilities). If thenetwork is not complete, method 300 proceeds to step 324, at which pointthe next segment is selected, and, from step 324, returns to 306 suchthat a P2P PW(s) may be provisioned for a physical link(s) connectingthe routers of the newly selected segment. If the network is complete,method 300 proceeds to step 326.

At step 326, a restoration protocol is run over the P2P PWs. At thispoint, the multicast protocol is running using the association of themulticast protocol to the IP interfaces. Thus, the configured network issimultaneously supporting both restoration capabilities and multicastcapabilities. At step 328, method 300 ends. Although depicted anddescribed as ending (for purposes of clarity), the configured networkcontinues to operate, thereby providing simultaneous support for bothrestoration capabilities and multicast capabilities.

FIG. 4 depicts a method according to one embodiment of the presentinvention. Specifically, method 400 of FIG. 4 includes a method forconfiguring a router in an IP network to support both fast restorationcapabilities and native multicast capabilities. Although depicted anddescribed herein as being performed serially, at least a portion of thesteps of method 400 may be performed contemporaneously, or in adifferent order than depicted and described with respect to FIG. 4. Themethod 400 begins at step 402 and proceeds to step 404.

At step 404, a P2P PW is established. The P2P PW has two endpoints (oneon the router being configured and one on another router adjacent to therouter being configured). At step 406, the P2P PW (i.e., the endpoint ofthe P2P PW on the router being configured) is associated with an IPinterface of the router being configured. At step 408, a multicastprotocol is associated with the IP interface on the router beingconfigured (i.e., the multicast protocol is bound to the IP interface).At step 410, method 400 ends.

In this manner, the router is configured to run both the restorationprotocol and the multicast protocol simultaneously over the P2P PW whileavoiding any of the problems previously resulting from running arestoration protocol and a multicast protocol together over an IPnetwork. Although depicted and described as ending, each of the routersin the network may be configured in this manner such that the networkmay simultaneously support both the restoration protocol and themulticast protocol.

FIG. 5 depicts a method according to one embodiment of the presentinvention. Specifically, method 500 of FIG. 5 includes a method forreacting to a failure in an IP network supporting both fast restorationand native multicast capabilities. Although depicted and describedherein as being performed serially, at least a portion of the steps ofmethod 500 may be performed contemporaneously, or in a different orderthan depicted and described with respect to FIG. 5. The method 500begins at step 502 and proceeds to step 504.

At step 504, a failure condition is detected. The failure condition isdetected at a first router. The failure condition may be any type offailure condition which may be detected at the first router (e.g., ahardware failure, a link failure, or some other failure condition hasoccurred and been detected at the first router).

A P2P PW exists between the routers. An IP interface on the first routeris associated with the endpoint of the P2P PW that terminates on thefirst router and an IP interface on the second router is associated withthe endpoint of the P2P PW that terminates on the second router. Arestoration protocol is running over the P2P PW. A multicast protocol isassociated with the IP interface on the first router and is associatedwith the IP interface on the second router.

At step 506, in response to detection of the failure condition,restoration is performed using the restoration protocol running on theP2P PWs. The first router determines the P2P PW(s) impacted by thefailure condition. The first router initiates rerouting of the P2P PW(s)associated with the failure condition using the restoration protocol.For purposes of clarity, restoration is described herein for one P2P PW,although this process may be repeated for each P2P PW impacted by adetected failure condition.

The P2P PW is rerouted using a secondary path between the first andsecond routers. The rerouting of the P2P PW restores communicationbetween the IP interface on the first router and the IP interface on thesecond router, thereby enabling restoration of the IP interfaces on therespective first and second routers before the failure condition isdetected by the multicast protocol.

Thus, as a result of the fast restoration of the IP interfaces using thererouting of the P2P PW, any multicast flows between the first routerand the second router continue to be supported without being impacted bythe failure condition. The IP interfaces on the respective first andsecond routers are restored such that the failure condition istransparent to the multicast protocol, and, thus, is transparent tomulticast flows transporting data between the first router and thesecond.

At step 508, method 500 ends. Although depicted and described as ending(for purposes of clarity), upon completion of the reroute of the P2P PW,the IP interfaces on the first and second routers are restored and themulticast protocol continues to operate without experiencing the failurecondition. Although depicted and described herein as ending (forpurposes of clarity), following clearing of the failure condition (e.g.,the second router is repaired, the physical link is repaired, and thelike), the network may or may not revert to the original configuration.

Although primarily depicted and described herein with respect toembodiments in which a single ring topology network is used to providerestoration and multicast capabilities, it will be appreciated that inorder to provide improved network connectivity for delivery ofinformation from content sources to subscribers, many such ring networksmay be interconnected to form ring-within-ring networks, therebyimproving network connectivity for delivery of information from contentsources to subscribers. An exemplary ring-within-ring network isdepicted and described herein in FIG. 6.

FIG. 6 depicts a high-level block diagram an exemplary ring-within-ringcommunication network. As depicted in FIG. 6, a plurality of routers 610₁-610 ₁₇ (collectively, routers 610) are connected and configured toform numerous ring networks, including ring networks within ringnetworks.

For example, as depicted in FIG. 6, routers 610 ₁, 610 ₅, 610 ₈, and 610₄ form a first ring and routers 610 ₅, 610 ₆, 610 ₁₀, 610 ₉, and 610 ₈form a second ring, and the first and second rings are interconnectedvia routers 610 ₅ and 610 ₈ such that routers of the first ring maycommunicate with routers of the second ring using a combination of thetwo rings (e.g., router 610 ₁ may communicate with router 610 ₁₀ via afirst path from router 610 ₁ to router 610 ₅ to router 610 ₆ to router610 ₁₀ or via a second path from router 610 ₁ to router 610 ₄ to router610 ₈ to router 610 ₉ to router 610 ₁₀.

Similarly, for example, as depicted in FIG. 6, routers 610 ₁, 610 ₅, 610₂, 610 ₆, 610 ₁₀, 610 ₉, 610 ₈, and 610 ₄ form a first ring and routers610 ₃, 610 ₇, 610 ₁₁, 610 ₁₃, 610 ₁₀, and 610 ₆ form a second ring, andthe first and second rings are interconnected via routers 610 ₆ and 610₁₀ such that routers of the first and second rings may communicate usinga combination of the two rings (e.g., router 610 ₁ may communicate withrouter 610 ₁₃ via a first path that traverses routers 610 ₁, 610 ₅, 610₂, 610 ₆, 610 ₃, 610 ₇, 610 ₁₁, and 610 ₁₃ or via a second path thattraverses routers 610 ₁, 610 ₄, 610 ₈, 610 ₉, 610 ₁₀, and 610 ₁₃).

In this manner, routers 610 may be connected and configured to formnumerous ring networks, including ring networks within ring networks,such that communications between any pair of routers may be supportedusing the present invention.

Although primarily depicted and described herein with respect toembodiments associated with IPTV networks, the present invention may beused to simultaneously support fast restoration capabilities and nativemulticast capabilities in IP networks providing various other types ofservices.

Although primarily depicted and described herein with respect to one P2PPW being associated with each physical link, in other embodiments one ormore of the physical links may have more than one P2P PW associatedtherewith.

Although primarily depicted and described herein with respect to one P2PPW being impacted by a failure condition, it will be appreciated thatmultiple P2P PWs may be impacted by a failure condition (e.g., dependingon the number of P2P PWs established for each physical link, the type offailure condition (e.g., a failure of a node may impact multiple P2PPWs), and the like, as well as various combinations thereof. Thus,multiple restoration processes may be performed in response to adetected failure condition where multiple P2P PWs are impacted by thefailure condition.

Although primarily depicted and described herein with respect to usingMPLS for fast restoration, various other protocols may be utilized toprovide fast restoration with native multicast in accordance with thepresent invention.

Although primarily depicted and described herein with respect to usingPIM for multicast, various other protocols may be utilized to providemulticast with fast restoration in accordance with the presentinvention.

FIG. 7 depicts a high-level block diagram of a general-purpose computersuitable for use in performing the functions described herein. Asdepicted in FIG. 7, system 700 comprises a processor element 702 (e.g.,a CPU), a memory 704, e.g., random access memory (RAM) and/or read onlymemory (ROM), a restoration/multicast control module 705, and variousinput/output devices 706 (e.g., storage devices, including but notlimited to, a tape drive, a floppy drive, a hard disk drive or a compactdisk drive, a receiver, a transmitter, a speaker, a display, an outputport, and a user input device (such as a keyboard, a keypad, a mouse,and the like)).

It should be noted that the present invention may be implemented insoftware and/or in a combination of software and hardware, e.g., usingapplication specific integrated circuits (ASIC), a general purposecomputer or any other hardware equivalents. In one embodiment, therestoration/multicast control process 705 can be loaded into memory 704and executed by processor 702 to implement the functions as discussedabove. As such, restoration/multicast control process 705 (includingassociated data structures) of the present invention can be stored on acomputer readable medium or carrier, e.g., RAM memory, magnetic oroptical drive or diskette, and the like.

It is contemplated that some of the steps discussed herein as softwaremethods may be implemented within hardware, for example, as circuitrythat cooperates with the processor to perform various method steps.Portions of the functions/elements described herein may be implementedas a computer program product wherein computer instructions, whenprocessed by a computer, adapt the operation of the computer such thatthe methods and/or techniques described herein are invoked or otherwiseprovided. Instructions for invoking the inventive methods may be storedin fixed or removable media, transmitted via a data stream in abroadcast or other signal bearing medium, and/or stored within a memorywithin a computing device operating according to the instructions.

Although various embodiments which incorporate the teachings of thepresent invention have been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatstill incorporate these teachings.

1. A method for supporting restoration and multicast at a router in anInternet Protocol (IP) network, comprising: establishing apoint-to-point pseudowire having an endpoint at the router, thepoint-to-point pseudowire adapted for supporting restoration in responseto a failure; associating the point-to-point pseudowire with an IPinterface; and associating a multicast protocol with the IP interface.2. The method of claim 1, wherein the point-to-point pseudowire isestablished over a physical link between the router and another router.3. The method of claim 1, wherein the point-to-point pseudowirecomprises a Multiprotocol Label Switching (MPLS) point-to-pointpseudowire.
 4. The method of claim 1, wherein the restoration comprisesfast restoration occurring in less than 50 ms.
 5. The method of claim 1,wherein the IP interface comprises a service-enabled IP interface. 6.The method of claim 1, wherein running the multicast protocol using theassociation of the multicast protocol to the IP interface gives anappearance that the multicast protocol is running natively on an IPlink.
 7. The method of claim 1, wherein the multicast protocol comprisesProtocol Independent Multicast (PIM).
 8. The method of claim 1, furthercomprising: in response to detecting a failure condition, initiating areroute of the point-to-point pseudowire using a secondary path, whereinrerouting of the point-to-point pseudowire is adapted to restore the IPinterface in response to the failure condition, thereby rendering thefailure condition transparent to the multicast protocol.
 9. The methodof claim 1, further comprising: repeating the establishing step and theassociating steps on each of a plurality of routers for each of aplurality of links between adjacent ones of the routers, wherein therouters are arranged in a ring topology.
 10. An apparatus for supportingrestoration and multicast in an Internet Protocol (IP) network,comprising: means for establishing a point-to-point pseudowire having anendpoint at the router, the point-to-point pseudowire adapted forsupporting restoration in response to a failure; means for associatingthe point-to-point pseudowire with an IP interface; and means forassociating a multicast protocol with the IP interface.
 11. A method,comprising: detecting a failure condition at a router supporting apoint-to-point pseudowire having an endpoint on the router, wherein thepoint-to-point pseudowire supports a restoration protocol, wherein an IPinterface on the router is associated with the point-to-pointpseudowire, wherein a multicast protocol is associated with the IPinterface; and initiating a reroute of the point-to-point pseudowire,wherein rerouting of the point-to-point pseudowire is adapted to restorethe IP interface in response to the failure condition, thereby renderingthe failure condition transparent to the multicast protocol.
 12. Themethod of claim 11, wherein the reroute of the point-to-point pseudowireis initiated using a secondary path.
 13. The method of claim 11, whereinthe point-to-point pseudowire is established over a physical linkbetween the router and another router.
 14. The method of claim 11,wherein the point-to-point pseudowire comprises a Multiprotocol LabelSwitching (MPLS) point-to-point pseudowire.
 15. The method of claim 11,wherein the restoration comprises fast restoration occurring in lessthan 50 ms.
 16. The method of claim 11, wherein the IP interface on therouter comprises a service-enabled IP interface.
 17. The method of claim11, wherein running the multicast protocol using the IP interface givesan appearance that the multicast protocol is running natively on an IPlink.
 18. The method of claim 11, wherein the multicast protocolcomprises Protocol Independent Multicast (PIM).
 19. An apparatus,comprising: means for detecting a failure condition at a routersupporting a point-to-point pseudowire having an endpoint on the router,wherein the point-to-point pseudowire supports a restoration protocol,wherein an IP interface on the router is associated with thepoint-to-point pseudowire, wherein a multicast protocol is associatedwith the IP interface; and means for initiating a reroute of thepoint-to-point pseudowire, wherein rerouting of the point-to-pointpseudowire is adapted to restore the IP interface in response to thefailure condition, thereby rendering the failure condition transparentto the multicast protocol.
 20. A network, comprising: a plurality ofnodes connected in a ring topology, adjacent ones of the nodes having atleast one link between them; wherein a point-to-point pseudowire isestablished for each link independent of each of the other links,wherein endpoints of the point-to-point pseudowires are associated withrespective IP interfaces on the respective routers between which thepoint-to-point pseudowires are established, wherein each point-to-pointpseudowire is adapted to enable restoration of the IP interfacesassociated with the point-to-point pseudowire using a restorationprotocol; wherein a multicast protocol is associated with the IPinterfaces on the respective nodes.